Ubiquitin-specific protease occurring in the brain and dna encoding the same

ABSTRACT

A ubiquitin-specific protease occurring in the brain and a DNA encoding it, which are useful for research on the molecular mechanism of the neuroplasticity expression and so on.

TECHNICAL FIELD

The present invention relates to a ubiquitin-specific protease occurring in the brain and a DNA encoding the same.

BACKGROUND ART

It is considered that the local protein synthesis using mRNAs distributed in dendrites plays an important role in maintaining the already expressed synaptic plasticity. The synthesis in the postsynaptic region is considered especially important, and search for mRNAs associated with the postsynaptic density (PSD) has been carried out (Mol. Brain Res., 72:147-157, 1999). However, functions remain unknown for many of them.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a protein considered to exist in PSD and a DNA encoding it, which are useful for research on the molecular mechanism of the neuroplasticity expression and so forth.

The inventors of the present invention succeeded in obtaining a full-length cDNA for one of mRNAs described in Mol. Brain Res., 72:147-157, 1999, of which functions are unknown, and elucidating the function of the expression product thereof, and thus accomplished the present invention.

The present invention provides the followings.

-   (1) A protein of the following (a) or (b): -   (a) a protein which has the amino acid sequence of SEQ ID NO: 2; -   (b) a protein which has an amino acid sequence of SEQ ID NO: 2     including deletion, substitution or addition of one or several amino     acid residues and has a ubiquitin-specific protease activity. -   (2) The protein according to (1), which has the amino acid sequence     of SEQ ID NO: 2. -   (3) A DNA which encodes the protein as defined in (1) or (2). -   (4) The DNA according to (3), which has the nucleotide sequence of     the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ     ID NO: 1. -   (5) A DNA of the following (a) or (b): -   (a) a DNA which has the nucleotide sequence of the nucleotide     numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1; -   (b) a DNA which hybridizes to a DNA having a nucleotide sequence     complementary to the nucleotide sequence of the nucleotide numbers     178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 under a     stringent condition and encodes a protein having a     ubiquitin-specific protease activity. -   (6) A DNA of the following (a) or (D); -   (a) a DNA which has the nucleotide sequence of the nucleotide     numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1; -   (b) a DNA which has a nucleotide sequence showing a homology of 85%     or more with respect to the nucleotide sequence of the nucleotide     numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 and     encodes a protein having a ubiquitin-specific protease activity. -   (7) A recombinant vector comprising the DNA as defined in any one     of (3) to (6). -   (8) A transformant obtained by transforming a host with the DNA as     defined in any one of (3) to (6). -   (9) A method for producing a ubiquitin-specific protease, which     comprises culturing the transformant as defined in (8) and     collecting a ubiquitin-specific protease expressed by the     transformant from culture. -   (10) An antibody directed to the protein as defined in (1) or (2). -   (11) An antibody directed to a peptide having the amino acid     sequence of the amino acid numbers 1022 to 1036 in the amino acid     sequence of SEQ ID NO: 2.

BRIEF EXPLANATION OF THE DRAWING

FIG. 1 shows (a) a structure of expression product and (b) detection of ubiquitin-specific protease activity (electrophoresis photograph).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, the present invention will be explained in detail.

Among the proteins of the present invention, the protein having the amino acid sequence of SEQ ID NO: 2 is a protein identified as a ubiquitin-specific protease existing in the brain, as described in the examples mentioned later. For a protein, existence of a mutant having the same function is expected, and such a mutant having the same function can be obtained by suitably modifying the amino acid sequence of the protein. Therefore, a protein having an amino acid sequence of SEQ ID NO: 2 including deletion, substitution or addition of one or several amino acid residues and having a ubiquitin-specific protease activity also falls within the scope of the protein of the present invention.

An amino acid sequence of a protein can be modified by modifying a DNA encoding the protein with a well-known means such as the site-specific mutagenesis method and expressing the DNA of which nucleotide sequence is modified. Furthermore, the ubiquitin-specific protease activity is an activity of specifically proteolysing a ubiquitinated substrate protein, and this activity can be measured by a known method (refer to, for example, EMBO J., 16:1519-1530, 1997). Therefore, whether a protein has the same function or not can be easily determined by those skilled in the art.

The protein of the present invention preferably has the amino acid sequence of SEQ ID NO: 2.

The protein of the present invention may be made into a fusion protein by fusion with another protein such as glutathione transferase (GST) or a His-tag.

The DNA of the present invention is a DNA encoding the protein of the present invention. An example of the DNA of the present invention is a DNA having the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1. This DNA is a DNA of which nucleotide sequence was determined in the examples mentioned later. For a gene, existence of another gene having a different nucleotide sequence, but encoding the same product, or an allelic gene encoding a mutant having the same function is expected, and a gene encoding the same product or the mutant having the same function can be obtained by modifying the nucleotide sequence. Therefore, a DNA having a nucleotide sequence analogous to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 and encoding a protein having a ubiquitin-specific protease activity also falls within the scope of the DNA of the present invention. Examples of DNA having the analogous nucleotide sequence include a DNA which hybridizes to a DNA having a nucleotide sequence complementary to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 under a stringent condition and a DNA which has a nucleotide sequence showing a homology of 85% or more with respect to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1.

Examples of the stringent condition include the conditions of hybridization in 2×SSC containing 0.1% SDS at 50° C. and subsequent washing in 2×SSC containing 0.1% SDS at 25° C. for 0.5 hour. The washing is preferably washing in 1×SSC containing 0.1% SDS at 60° C. for 0.5 hour.

The homology is represented with a value calculated by using Genetryx (Software Development Co., Ltd.).

The DNA having the nucleotide sequence analogous to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 can be obtained by subjecting a DNA having the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 or a host harboring such a DNA to a mutagenesis treatment and selecting a DNA hybridizing under the aforementioned stringent condition or having a homology within the above-defined range from the obtained transformants. The method for measuring the ubiquitin-specific protease activity is known as described above, and therefore it is easy for those skilled in the art to select a DNA encoding a protein having the ubiquitin-specific protease activity from such DNAs.

The DNA of the present invention can be obtained in a conventional manner on the basis of the nucleotide sequence elucidated herein. For example, it may be synthesized by a chemical synthesis method or may be obtained by the reverse transcription PCR method using suitably designed primers from mRNAs prepared from cells or tissues expressing the ubiquitin-specific protease of the present invention.

The vector of the present invention is a recombinant vector containing the DNA of the present invention. The vector of the present invention can be obtained by inserting the DNA of the present invention into a vector in a conventional manner. The vector to which the DNA of the present invention is inserted is not particularly limited, and its examples include those usually used as cloning vectors and those usually used as expression vectors for mammalian cells. When the vector is used for the purpose of producing the protein of the present invention, an expression vector is especially useful.

The transformant of the present invention is a transformant obtained by transforming a host with the DNA of the present invention, and it expresses the protein of the present invention.

The host is not particularly limited, and its examples include animal cells, bacterial cells, yeast cells, insect cells and so forth. The transformation can be carried out in a conventional manner, and it is preferably carried out by introducing the vector of the present invention.

The production method of the present invention is a method for producing the protein of the present invention, i.e., a ubiquitin-specific protease, and it comprises culturing the transformant of the present invention and collecting a ubiquitin-specific protease expressed by the transformant from culture.

The culturing can be carried out under a condition that allows the transformant to express the protein of the present invention, and the collection of the protein of the present invention from the culture can be attained by a suitable combination of methods usually used for purification of proteins such as various chromatography techniques, electrophoresis and gel filtration. When the protein of the present invention is expressed as a fusion protein with GST or His-tag, the fusion protein can be purified by using a glutathione-Sepharose column or nickel-Sepharose column, respectively.

The antibody of the present invention is an antibody directed to the protein of the present invention, and it is preferably an antibody directed to a peptide having the amino acid sequence of the amino acid numbers 1022 to 1036 in the amino acid sequence of SEQ ID NO: 2 (also referred to as the “C-terminus peptide” hereinafter). In this specification, the term “antibody directed to” means an antibody that immunologically reacts.

The antibody of the present invention can be obtained from an animal immunized with the protein of the present invention (preferably, the C-terminus peptide). If it is a polyclonal antibody, it can be prepared from blood serum of the immunized animal. If it is a monoclonal antibody, it can be prepared by fusing an antibody-producing cell obtained from the spleen or lymph node of the immunized animal with a myeloma cell and selecting a hybridoma that produces an antibody showing strong specificity to the protein of the present invention (preferably, the C-terminus peptide).

As the immunogen, a fragment of the protein of the present invention obtained according to the production method of the present invention can be used. Alternatively, an antigen synthesized on the basis of the aforementioned amino acid sequence can be used. The antigen may be used as a complex with a carrier protein. Various linking agents can be used for the preparation of the complex of the antigen and the carrier protein, and glutaraldehyde, carbodiimide, maleimide active ester and so forth can be used. The carrier protein may be selected from those conventionally used such as bovine serum albumin, thyroglobulin and hemocyanin, and a method of coupling it in a ratio of 1- to 5-fold amount is used.

The animal used for immunization may be mouse, rat, rabbit, guinea pig, hamster or the like, and inoculation may be carried out by subcutaneous, intramuscular, intraperitoneal administration or the like. Upon the administration, the antigen for immunization may be mixed with complete Freund's adjuvant or incomplete Freund's adjuvant and then administered. The administration is usually carried out every 2 weeks to 5 weeks. An antibody-producing cell obtained from the spleen or lymph node of the immunized animal is fused to a myeloma cell and isolated as a hybridoma. As the myeloma cell, those derived from mouse, rat, human and so forth are used. Although it is preferably a myeloma cell derived from the same species as that from which the antibody-producing cell is derived, it may be a heterozoic cell.

The cell fusion can be carried out according to a known method, for example, the method of Koehler and Milstein (Nature, 256, 495, 1975). As a cell fusion promoting agent, polyethylene glycol, Sendai virus or the like can be mentioned, and the cell fusion can be usually carried out by a reaction for about 1 to 10 minutes using polyethylene glycol (average molecular weight: 1000 to 4000) at a concentration of about 20 to 50% at a temperature of 20 to 40° C., preferably 30 to 37° C., usually with a number ratio of antibody-producing cells and myeloma cells of about 1:1 to 10:1.

For screening for antibody-producing hybridoma, various immunochemical methods can be used. Examples thereof include ELISA (enzyme-linked immunosorbent assay) method using a microplate coated with the protein of the present invention (preferably, the C-terminus peptide), EIA (enzyme immunoassay) method using a microplate coated with an anti-immunoglobulin antibody, immonoblotting method using a nitrocellulose membrane to which electrophoresed sample containing the protein of the present invention (preferably, the C-terminus peptide) is transferred and so forth.

From a well thus screened, cloning is further carried out by, for example, limiting dilution analysis to obtain clones. Selection and culture of hybridoma are usually carried out with a medium for animal cells (e.g., RPMI1640) supplemented with HAT (hypoxanthine, aminopterin and thymidine) and containing 10 to 20% of bovine fetal serum. The clones obtained as described above can be transplanted into the abdominal cavity of SCID mouse to which pristine is preliminarily administered, and after 10 to 14 days, the ascites containing monoclonal antibodies at a high concentration can be extracted and used as the raw material for purification of the antibodies. Moreover, it is also possible to culture the clones and use the culture broth as the raw material for purification of the antibodies. For the purification of monoclonal antibodies, a method known as a purification method of immunoglobulin can be used, and the purification can be easily attained by, for example, ammonium sulfate fractionation, PEG fractionation, ethanol fractionation, use of anion exchanger, affinity chromatography using the protein of the present invention (preferably, the C-terminus peptide) or the like. Purification of polyclonal antibodies from blood serum can also be carried out in a similar manner.

As the monoclonal antibody, a fraction of Fab′ or Fab in which Fc′ or Fc region is removed, or a polymer thereof may be used. Moreover, a chimeric antibody or humanized antibody thereof may also be used.

By an immunological method using the antibody of the present invention, the protein of the present invention in a biological sample can be qualitatively or quantitatively determined. As the immunological method, known methods such as immunostaining method, enzyme immunoassay, agglutination method, competitive immunoassay and sandwich assay can be applied for a biological sample subjected to a suitable treatment, for example, separation of cells, extraction etc. as required. The immunostaining method can be carried out by, for example, the direct method using a labeled antibody, indirect method using a labeled antibody directed to the antibody or the like. As the labeling agent, any of known labeling agents such as fluorescent substances, radioactive substances, enzymes, metals and dyes can be used.

EXAMPLES

Hereafter, the present invention will be explained more specifically with reference to the following examples.

Example 1 Cloning of Full Length Dem 21 cDNA

The Dem 21 double-stranded cDNA (length: 215 bp) was obtained as reported in Mol. Brain Res. 72:147-157, 1999. The obtained cDNA was labeled with digoxigenin (DIG) by the PCR labeling method to obtain a DIG-labeled Dem 21 cDNA probe.

In screening libraries prepared from unstimulated rat brains by using this probe, any positive clone was not obtained. Therefore, an oligo-(dT) primed cDNA library prepared from a hippocampus harvested 4 hours after high-frequency stimulation was screened.

The oligo-(dT) primed cDNA library prepared from hippocampus harvested 4 hours after high-frequency stimulation in rats pretreated with cyclohexamide (Neuron, 14:433-455, 1995) was kindly provided by Dr. Yamagata of Tokyo Metropolitan Institute for Neuroscience. This library was plated at a density of 5×10⁴ plaques per 150-mm plate, and filters (membranes) on which the plates were duplicated were screened by hybridization to the DIG-labeled Dem 21 cDNA probe. The hybridization was carried out overnight at 42° C. in the DIG Easyhyb buffer. The membranes were washed twice with 2×SSC containing 0.1% SDS at room temperature and then washed with 1×SSC containing 0.1% SDS at 65° C. for 15 minutes. Color development was carried out according to the instruction of the DIG Chemical Color Development Kit (Nippon Roche). Candidate plaques were selected, and re-screening was carried out in a similar manner. Inserts of positive cDNA clones were excised and confirmed by DNA sequencing. As a result, two of partially overlapped positive clones with different lengths, both of which had the probe sequence, were obtained (18′2 and 17′1). The clone 18′2 contained a poly(A)⁺ sequence and an insert of 2163 bp having AAATTAAA polyadenylation signal upstream from the poly(A)⁺ by 30 bp. The clone 17′1 contained an insert of 4369 bp having the same 3′ sequence as that of the clone 18′2.

Since the longer clone contained a partial open reading frame (ORF), 5′ RACE was carried out in order to obtain the full length cDNA of Dem21, to obtain a further 5′ sequence. Specifically, synthesis of a single-stranded cDNA for mRNA (0.5 μg) prepared from the brain of rats treated with kainic acid by a reverse transcription reaction, cyclization of the obtained cDNA, and PCR by using the cyclized cDNA as a template were carried out twice by using 5′ Full Race Core Set and Taq DNA polymerase (both from Takara Shuzo). In the first 5′ RACE, a gene-specific primer for a reverse transcription reaction (SEQ ID NO: 4) and an antisense primer and a sense primer for PCR (SEQ ID NOS: 5 and 6), which were prepared on the basis of the cDNA sequence of 17′ 1, were used. In the second 5′ RACE, a gene-specific primer for a reverse transcription reaction (SEQ ID NO: 7) and an antisense primer and a sense primer for PCR (SEQ ID NOS: 8 and 9), which were prepared on the basis of the nucieotide sequence obtained by the first 5′ RACE, were used.

By the first 5′ RACE, a 1.0-kb fragment overlapping the 5′ portion of the clone 17′1 was obtained. Furthermore, by the second 5′ RACE, a 800-bp fragment overlapping the fragment obtained by the first 5′ RACE was obtained. By combining the cDNA sequence of 17′1 and the sequences obtained by 5′ RACE, cDNA of 5738 bp was obtained. The nucleotide sequence thereof is shown in SEQ ID NO: 1. This 5738 bp sequence contained ORF of 3111 bp. As described above, the poly(A)⁺ tail was preceded by a consensus AAATTAAA polyadenylation signal. The 5′ portion of 178 nucleotides from the 5′ end of the putative initiation codon was rich in GC, and was consistent with the 5′ untranslation region. The flanking nucleotide sequence around the putative initiation codon was consistent with the Kozak consensus sequence (J. Biol. Chem., 266:19867-19870, 1991) with Gs at −3 and +4. The presence of a CT-rich sequence and an in-frame stop codon upstream of the putative initiation codon further verified that the ATG was a real initiation codon. From the above, it was found that the obtained cDNA of 5738 bp contained the full length cDNA of Dem 21, and the fragment of 215 bp reported in Mol. Brain Res., 72:147-157, 1999 was the 3′ end of the full length cDNA having the poly (A)⁺.

A homology search of the deduced amino acid sequence of the full length Dem 21 cDNA clone (SEQ ID NO: 2) with the DDBJ nr database did not show an identical protein or any protein species with strong similarities. However, the deduced protein contained many domains in which Cys box, His box, Asp box, KRF box etc. observed in the ubiquitin-specific protease (USP) were conserved. On the basis of this characteristic, Dem 21 was considered to be a novel member of the USP family enzymes, and therefore Dem 21 was named synaptic USP (synUSP). Among the known USPs, synUSP is the most similar to HAUSP (herpesvirus related ubiquitin-specific protease), which is named USP7 according to the nomenclature proposed by the Human Genome Organization (HUGO) Nomenclature Committee (http://www.gene.ucl.ac.uk/nomenclature). Between two of these proteins, there was 28% identity and 40% similarity for 413 amino acid residues.

synUSP encodes a protein of 1036 amino acid residues and has a predicted molecular mass of 118.78 kDa and pI of 5.83. In the database search, besides the USP active site domain, a leucine zipper domain was detected in the carboxyl terminus region. Since the leucine zipper domain is suggested to be involved in a protein-protein interaction, the carboxyl terminus of synUSP may participate in a certain type of protein-protein interaction. synUSP also has two repeats of 6 amino acid residues ((L/I)LCPHG (SEQ ID NO: 3)) in the carboxyl terminus portion. In the database search, any information about the function of this sequence was not obtained.

Example 2 Confirmation of USP Activity of Expression Product

The activity of synUSP for digesting a model ubiquitinated protein was investigated by using a co-expression system of E. coli.

The USP activity was measured basically following the method of Everett et al. (EMBO J., 16:1519-1530, 1997) by using a T7-driven IPTG-inducible synUSP expression plasmid. The pT7-synUSP plasmid was prepared by inserting the complete coding region of synUSP into the NcoI site of T7 expression plasmid pET3d (pBR322 Amp^(r) replicon). pACT7-synUSP which is a plasmid containing a T7-synUSP expression cassette in pACYC184 Cm^(r) replicon was constructed by inserting an EcoRV fragment of pT7-synUSP at the EcoRV site of pACYC184. A plasmid pACYC-UBP (PACYC184 Cm^(r) replicon) encoding yeast UBP2 and a plasmid pGEX-Ub52 (pBR322 Amp^(r) replicon) encoding a GST-Ub52 fusion protein were used as positive controls for USP and a USP substrate. For cleavage of the GST-Ub52 substrate, cells of the E. coli strain BL21 (DE3) harboring pGEX-Ub52 were transformed with either pACT7-synUSP or pACYC-UBP2, and colonies resistant to both of ampicillin and chloramphenicol were grown-up. The protein expression was induced by IPTG, and the cells were further incubated for 3 hours to allow USP to cleave the substrate. The cells were sonicated to prepare an extract of water-soluble proteins. The GST fusion protein and proteolysed products thereof were purified by using glutathione-agarose beads, subjected to SDS-polyacrylamide gel electrophoresis and detected by staining with Coomassie brilliant blue. Further, similar procedure was carried out for synUSP in which Cys98 was replaced with Ala and synUSP of which C-terminus sequence was deleted from either the His box, LLCPHG repeat sequence or leucine zipper (FIG. 1, a).

The results are shown in FIG. 1, b. The expression of GST-Ub52 substrate protein was induced by IPTG (Lane 1). The GST-Ub52 protein was degraded to a band of 30 kDa by the co-expression of yeast USP2. The size of the degradation product was good agreement with that calculated. Therefore, the validity of the aforementioned USP activity assay system was confirmed. When a wild type (WT) synUSP was co-expressed, the amount of the GST-Ub52 protein of 45 kDa decreased, and the proteolysis product of 30 kDa markedly increased along with it (Lane 3). Therefore, it was confirmed that synUSP has the USP activity. The activity of synUSP disappeared by either replacing Cys98 with Ala or deleting the C-terminus sequence from the His box, LLCPHG repeat sequence or leucine zipper (Lanes 4 to 7).

Example 3 Preparation of Antibody, Subcellular Distribution and Tissue Distribution of synUSP

A peptide (C-15 peptide) consisting of 15 amino acid residues of the C-terminus of synUSP (amino acid numbers 1022 to 1036 in the amino acid sequence of SEQ ID NO: 2) was coupled to keyhole limpet hemocyanin and used to immunize a rabbit. After repeating booster immunization, blood serum was collected and anti-synUSP antibodies (C-15 Ab) were purified by affinity chromatography using Affi-Gel 10 on which the C-15 peptide was immobilized.

Specificity of the purified C-15 Ab was examined by performing Western blotting to the full length synUSP expressed in Cos7 cells according to the method described in J. Biol. Chem., 276, 21417-21424 (2001). As a result, C-15 Ab specifically reacted with the expressed synUSP of 125 kDa, and this interaction was blocked by addition of an excessive amount of the C-15 peptide.

The subcellular distribution of synUSP was investigated by using C-15 Ab. A subcellular fraction was obtained as follows. As described in Mol. Brain Res., 78, 80-90 (2000), fractions of synaptic plasma membrane (SPM) and PSD were obtained from the forebrain of Wistar rat (six-week old, male). Further, during the isolation of PSD, P1 (fraction containing nuclei and cell debris), P2 (crude mitochondrion fraction) and syn (synaptosome fraction) were obtained. Furthermore, a soluble fraction and a dendritic lipid raft fraction were obtained as described in Mol. Brain Res., 78, 80-90 (2000) and Mol. Brain Res., 89, 20-28 (2001), respectively.

Each fraction was analyzed by Western blotting using C-15 Ab. As a result, a band of the same molecular weight as the full length synUSP expressed in the Cos7 cells was detected in the total homogenate, soluble, dendritic lipid raft and PSD fractions. In the PSD fraction, immunoreactive bands with different sizes were detected. However, since the bands disappeared by the addition of C-15 peptide and the amounts of the bands fluctuated in every experiment, they appeared to be degradation products of synUSP.

Western blotting was carried out in the same manner as that described above for proteins prepared from the heart, brain, spleen, lung, liver, skeletal muscle, kidney, testis, thymus gland, stomach and small intestine. As a result, a band of 125 kDa was detected in the brain and thymus gland, and the expression level in the thymus gland was lower than that that in the brain. Moreover, a band of the same size was detected also in the testis. However, the expression level was extremely low. In the brain, immunoreactive band smaller than the full length was detected. However, since these bands disappeared by the addition of C-15 peptide and the amounts of the bands fluctuated in every experiment, they appeared to be degradation products of synUSP. Further, two immunoreactive bands were detected in a low molecular weight region also in the liver. These bands disappeared by the addition of C-15 peptide. No immunoreactive band was detected in the other tissues.

INDUSTRIAL APPLICABILITY

According to the present invention, a ubiquitin-specific protease and a DNA encoding it are provided. These are useful for researches on neuroplasticity and pathology of neurodegenerative disorders. 

1. A protein of the following (a) or (b): (a) a protein which has the amino acid sequence of SEQ ID NO: 2; (b) a protein which has an amino acid sequence of SEQ ID NO: 2 including deletion, substitution or addition of one or several amino acid residues and has a ubiquitin-specific protease activity.
 2. The protein according to claim 1, which has the amino acid sequence of SEQ ID NO:
 2. 3. A DNA which encodes the protein as defined in claim 1 or
 2. 4. The DNA according to claim 3, which has the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO:
 1. 5. A DNA of the following (a) or (b): (a) a DNA which has the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1; (b) a DNA which hybridizes to a DNA having a nucleotide sequence complementary to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 under a stringent condition and encodes a protein having a ubiquitin-specific protease activity.
 6. A DNA of the following (a) or (b): (a) a DNA which has the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1; (b) a DNA which has a nucleotide sequence showing a homology of 85% or more with respect to the nucleotide sequence of the nucleotide numbers 178 to 3285 in the nucleotide sequence of SEQ ID NO: 1 and encodes a protein having a ubiquitin-specific protease activity.
 7. A recombinant vector comprising the DNA as defined in any one of claims 3 to
 6. 8. A transformant obtained by transforming a host with the DNA as defined in any one of claims 3 to
 6. 9. A method for producing a ubiquitin-specific protease, which comprises culturing the transformant as defined in claim 8 and collecting a ubiquitin-specific protease expressed by the transformant from culture.
 10. An antibody directed to the protein as defined in claim 1 or
 2. 11. An antibody directed to a peptide having the amino acid sequence of the amino acid numbers 1022 to 1036 in the amino acid sequence of SEQ ID NO:
 2. 